The present invention generally relates to an automobile exhaust gas purifying device and, more particularly, to a casing structure for a catalytic converter of the radial flow type.
Various types of radial-flow catalytic converters for substantially purifying exhaust gases emitted from an automobile combustion engine are well known to those skilled in the art and are currently commercially installed in automobile exhaust systems, an example of which is schematically shown in FIG. 1 of the accompanying drawings in longitudinal sectional view. Referring first to FIG. 1, the illustrated prior art catalytic converter 10 is shown as disposed between an outlet of the exhaust manifold 11 and an exhaust pipe 12 and located in the vicinity of and laterally of the automobile internal combustion engine E with its longitudinal axis oriented vertically. The catalytic converter 10 comprises a generally cylindrical double-walled enclosure 13 having an annular container 14 coaxially positioned inside the double-walled enclosure 13. The annular container 14 is for accommodating therein a catalyst material M and is comprised of a cylindrical perforated inner sleeve 15 and a cylindrical perforated outer sleeve 16. These inner and outer sleeves 15 and 16 have their respective first ends closed by a common end plate 17 and their respective second ends welded to the inner and outer peripheral faces of an annular flange member 18 adapted to be connected to a mating flange 11a of the exhaust pipe 11.
The double-walled enclosure 13 having the annular container 14 disposed therein in coaxial relation thereto has its first end rigidly connected to an annular flange member 19 adapted to be connected to a mating flange 12a of the exhaust pipe 12 and its second end welded to the outer peripheral face of the annular flange member 18 together with the second end of the outer sleeve 16.
The catalytic converter of the construction shown in FIG. 1 is so designed that exhaust gases of relatively high temperature emitted from the automobile internal combustion engine E and supplied to the converter through the exhaust manifold 11 can flow into the inner chamber inside the perforated inner sleeve 15 and then into a generally annular chamber outside the perforated outer sleeve 16 and inside the double-walled enclosure 13 after having passed through the bed of the catalyst material M contained in the annular intermediate chamber between the perforated inner and outer sleeves 15 and 16, the exhaust gases within the annular chamber outside the perforated outer sleeve 16 and inside the double-walled enclosure 13 being subsequently discharged to the atmosphere as substantially purified exhaust gases.
U.S. Pat. No. 4,124,357 discloses a catalytic converter casing utilizing a generally cylindrical double-walled enclosure which is comprised of generally cylindrical outer and inner shells with an annular space defined therebetween, each of said outer and inner shells of the double-walled enclosure being constituted by a pair of substantially semicircular-cross-section shell halves. Each semicircular-cross-section shell half has a pair of opposed side flanges extending lengthwise thereof and transversely protruding in opposite directions to each other. This double-walled enclosure is, in the assembled condition, of such a construction that the respective pairs of the side flanges of the inner shell halves are connected to each other and extend radially outwardly of the cylindrical inner shell in the opposite directions with respect to each other thereby dividing the annular space into two semicylindrical space sections, said respective pairs of the side flanges of the inner shell halves being in turn sandwiched firmly between the corresponding pairs of the side flanges of the outer shell halves which are connected to each other to form the cylindrical outer shell.
Since the catalytic converter for automobile use is generally operated under a condition not only of elevated temperature, but also vibrations which may be generated by the combustion engine being operated and/or by the running of an automobile on an irregular road surface, the direction in which a particular physical force, which may bring about damage to the catalytic converter casing, acts on the catalytic converter casing is not fixed. By way of example, as is well known to those skilled in the art, during the operation of the internal combustion engine, not only does the engine vibrate as a result of a movement of the crankshaft, but also it tends to undergo a rolling motion when the power torque of the engine varies as a result of the foot-controlled adjustment of the acceleration pedal. In addition, the engine vibrates as the vehicle runs on an irregular road. In view of this, the catalytic converter is required to be durable so as to withstand the complex vibrations which may be transmitted from the engine proper and also from the vehicle superstructure to the catalytic converter.
Where the catalytic converter is mounted in the vicinity of the combustion engine with the inlet port of the catalytic converter coupled directly to the outlet port of the exhaust manifold such as shown in FIG. 1, some of the various welded joints employed in any one of the prior art catalytic converters tend to be adversely affected by the complex vibration of the engine. In particular, where the catalytic converter is supported by the exhaust manifold, fixed to the engine proper, and by the exhaust pipe, fixed to the vehicle superstructure, at a position laterally of the engine proper with its longitudinal axis oriented vertically, there is the possibility that, as the engine undergoes the rolling motion, one end portion of the catalytic converter adjacent the engine proper tends to be pulled outwardly relative to the opposite end portion thereof. Moreover, there is also a possibility that the catalytic converter will undergo a substantial pivotal or swivel motion about the point of connection of the catalytic converter to the exhaust manifold. The worst that may happen is the possible detachment of the catalytic converter from the exhaust manifold, and also a possible breakage of the converter casing which may in turn bring about a possible breakage of the annular container inside the double-walled enclosure.